1. Field of the Invention
The present invention relates to a method and system for automated training of manual skills. More specifically, the invention relates to a method and system wherein body motion of a subject being trained is measured so as to derive a set of motion variables, the motion variables are compared to a reference motion to derive a motion error value, the motion error value is compared to a threshold error value corresponding inversely to the proficiency level of the subject, and a training signal is provided to the subject whenever the motion error value exceeds the threshold error value.
Manual tasks are defined as all tasks where the human being inputs some type of control and obtains feedback information as to the result of that control effort. Included in the category of manual tasks are tasks performed with the arms, hands, or other limbs. Also included are tasks performed with the aid of machines or tools to provide mechanical advantage, accuracy, speed, force, or stability. Manual tasks are found in everyday life such as assembling items, placing objects or shelves, opening doors, etc.; in sports, such as rolling bowling balls, shooting arrows, hitting golf balls, shooting basketballs, throwing footballs, etc.; and in work, such as operating folklifts, hammering nails, operating machines, and so forth. Manual tasks are also important in military operations--a few examples are aiming rifles or other weapons, flying aircraft, and controlling ships. The list of examples of manual tasks, for practical purposes, is endless.
A manual task consists of a set of parallel of sequential actions intended to produce a desired result. Evaluation of a manual effort typically consists of an evaluation of the net result of the effort. For example, evaluation of a dart throw is accomplished by observing how far the dart is displaced from the desired location when it comes to rest. Evaluation of a bowling roll might be measured in terms of the number of pins remaining or whether or not the bowling ball hit the intended pin. This type of measure is termed a "summary measure" since it summarizes the result of the total effort in one measurement.
A summary measure is available only after the task is completed and often only after some time has elapsed. For example, for a golf stroke, the measure of performance might be the distance from the pin to the ball after it comes to rest; however, the flight time of the ball is such that information for evaluation is not available until well after the manual effort has been completed. For some manual tasks, performance information may be available a short time after the task has been completed and, for others, information is available only after a very long time after the task is completed.
As stated above, a summary evaluation of a task necessarily combines the effect of all task component actions, and provides the evaluation only after all component actions are complete. This lack of specificity and the time delay prohibit rapid acquisition of manual skill. If the effect on task performance of each component action is evaluated and that performance information fed back to the performer, each component action can be learned as in entity. This specificity promotes rapid training.
Of at least equal importance to training efficiency is the time delay between the completion of a component action and its evaluation. Numerous studies (for example, the work described by I. M. Bilodeau, Information Feedback, New York: Academic Press, 1966, Chapter 6) have shown that the greater the delay before evaluation information is fed back to the trainee, the lower the learning rate. If a continuous and instantaneous evaluation of performance is available, performance of each component action can be evaluated during the performance and immediately upon its completion. This information, properly fed back to the trainee, eliminates both the non-specificity and time delay problems, and permits rapid learning of the skills required to perform the manual task.
There are several problems to be considered in the presentation of performance information to the trainee. The performer, a human being, can receive and use only a limited amount of information in a given time period. Selection of only important information and modulation of the information rate to match the trainee's useful receiving rate are required. Another problem is that, if performance information is not fed back correctly, the performer may learn to rely on the feedback information to perform, rather than use it to learn to perform. A still further problem is that the human sensory channel used to receive the performance evaluation information must be selected in conjunction with considering the information as imposed by the component action itself. Solutions to these problems are embedded in the automated training techniques used and, therefore, are best discussed after the techniques have been described.
To summarize, the purpose of the presently disclosed invention is to provide rapid training of skills for manual tasks to a high level of task performance. A key feature of the invention is that performance is evaluated continuously, and that performance information can be presented to the performer in several ways, including immediate feedback to the performer or to the coach. The evaluation information allows the performer to identify both correct and incorrect component actions, and possibly to correct the action while it is being performed.
The primary application of the present invention is improvement in the speed of learning manual control skills, and improvement in the level and consistency of the performance attained. An additional application relates to the continuous testing of operators, such as machinery operators, so that performance can be evaluated continuously in order to determine the need for retraining to maintain performance, to improve safety, or to change motivation factors.
In order to distinguish the automated training techniques described herein from other training techniques, it is useful to recognize that the method is composed of two parts: (1) the continuous measurement and processing of measure signals to provide a continuous performance evaluation; and (2) the feedback techniques used to direct performance information to the performer. It is necessary, as is shown below, to modulate the amount of information fed back to the performer, depending on the task and his skill level because he can absorb and use only a limited amount of information during any time interval.
2. Description of Prior Art
There has been considerable work accomplished in a related field known by a variety of terms, the major term being "adaptive training." This approach to training of manual skills was pioneered by Kelly et al ("A Manual for Adaptive Techniques," Final Report, August 1970, AD-711-985), and has been used by many others to implement automatic training systems. Essentially, the technique is to start the trainee on a very simple problem, and, depending on how well he performs on that problem, the trainee is given successively more difficult tasks to perform. Adaptive logic determines the degree of difficulty of the next problem as a function of the student's immediate past performance. For example, should his performance degrade, the adaptive logic decides whether he should receive an easier task or receive additional tasks at the present problem difficulty level. Typically, the trainee is given tasks which are successively more difficult until he reaches the criterion performance, whereupon the program is terminated.
There are several well-known advantages to this type of training. One is that the training tasks are adapted to the trainee's performance so that he is not over-loaded with very difficult and perhaps unmanageable tasks in the beginning. Also, as Kelly has stated, the technique is especially applicable to research of human control capability, since the adaptive nature of the equipment forces the system (man and machine) to a region where performance is limited. In this way, the researcher is not burdened with collecting data in situations where high performance is easy, but rather collects data where the human being is stressed to provide high performance.
However, there are several difficulties with the adaptive training method. The major difficulty is that the control problem is modified by either increasing or decreasing task disturbances, or by changing the properties of the task itself. These modifications change the control task from the initial one to the final one, and thus the trainee has the problem of learning to perform a variety of tasks and to operate with a variety of disturbances during the training program. These "interim" tasks and disturbances may not correspond to any of the real life problems the operator may encounter after training is completed.
Another difficulty, which is related to the first, is that the trainee is not given continuous performance information, and even if he were, he would not be able to apply it effectively because of the change (typically a step-wise change) in control problem environment. Thus, with this system, the trainee may learn basic skills, but is prevented from tackling the real problem directly. The invention described here is distinctive in that it employs fixed tasks and disturbance profiles, but varies criterion performance as a function of performance achievement by the trainee.
There have been numerous studies where knowledge-of-results (KR) has been used to improve both the learning rate and level of performance when training is completed. Of interest here is the technique known as "biofeedback," (Roberts et al, "Voluntary Control of Skin Temperature: Unilateral Changes Using Hypnosis and Feedback," Journal of Abnormal Psychology, Vol. 28, No. 1, 1973). With this technique, a signal is fed back when performance (which, in some studies, is controlled by an involuntary response) is out of tolerance. Yet experimental results show that the feedback does result in effective training of the control response desired. The unfortunate property of this technique is that the feedback is triggered by the effect of a control error (which occurs after the error) instead of being triggered by the error itself. However, results of this research suggest that a very simple form of performance feedback, a binary out-of-tolerance signal, can indeed be used to control specific responses.